Micro-electromechanical systems (MEMS) are used in a variety of applications such as optical display systems. Such MEMS devices have been developed using a variety of approaches. In the case of light modulator devices, the device converts white light into color light through Fabry-Perot interference between a variable height, partially reflecting pixel plate, and a fixed reflector bottom plate. The gap between the pixel plate and bottom reflector is controlled by a balance of forces between an electrostatic field and elastic deformation of pixel flexures.
The electrostatic field is produced by a voltage or charge difference between the conductive pixel plate and the conductive bottom capacitor plate. The electrostatic field pulls the pixel plate towards the bottom capacitor plate. Frequently, long, thin flexures span between fixed posts and the pixel plate. These flexures deform elastically as the pixel plate is electrostatically attracted to the bottom plate capacitor. When the voltage or charge difference between the pixel plate and bottom plate capacitor is removed, the stored elastic energy in the flexures returns the pixel plate to its original position.
To maximize the optical efficiency of the original Fabry-Perot device, the interconnect vias are stacked on top of each other to reduce their footprint on the bottom reflector level. Stacked vias are generally not considered a best practice for Integrated Circuit (IC) design and manufacturability, because the aspect ratio of the holes can increase beyond the ability to properly fill and clear.